1. Field of the Invention
This invention relates to the distribution of protected digital audio data. More particularly, the invention relates to the creation and use of a protected audio compact disc.
2. Description of the Related Art
The compact disc continues to be a very popular media type for distributing digital audio content. However, in recent years, technologies have developed, such as compact disc-read-only memory (“CD-ROM”) drives and the Moving Pictures Expert Group (“MPEG”), audio layer 3 (“mp3”) data format, which allow quick copying of the audio data contained on most compact discs into formats that can be easily shared over the Internet to thousands of people. These technologies allow non-paying users to access and distribute the audio content cheaply and with virtually no limitations. This reduces the incentives to produce the audio content and threatens a social cost as fewer content producers are willing to take the risk of theft by releasing their work for sale on compact disc.
Existing systems, such as one developed by Macrovision, attempt to solve this problem by incorporating technology onto audio compact discs that prevents the discs from being read by a computer CD-ROM drive but yet still allows them to be read by traditional audio compact disc players. While this technology does help prevent rampant copying of compact discs, it has the unfortunate effect of preventing audio content purchasers from accessing their legally-acquired audio content through their computers. With existing systems, if the audio data cannot be read by a computer, it cannot be used for allowed purposes, such as storage on the computer's hard drive for backup or playback purposes or transfer to a portable digital audio device. With the increased usage of computers and portable audio devices, limitations such as these can severely hurt the commercial viability of such a protected CD.
What is needed is a system that prevents unlicensed copying of audio data from a CD, but that still allows authorized forms of computer-related access to purchasers.